Catalytic reactions involving gaseous reactants are often conducted in fixed-bed chemical reactors filled with an appropriate catalyst. Because of the high mobility of gas, the fixed-bed reactors designed for gaseous reactants typically consist of a multiplicity of long, small bore tubes, each in the form of a packed tubular reactor, in order to provide the resident time required to achieve a desired reaction yield and minimize the extent of undesired channelling. An ideal tubular reactor is designed such that it approximates a plug flow type reactor with minimum amount of mixing, and each reactant molecule travels approximately the same length in the reactor.
A typical tubular reactor for gaseous reactants can be only several inches in diameter, but many feet long. Because of the great dimensional asymmetry of tubular reactors and the relative high cost of construction thereof, it is desirable to modify a tank- or vessel-type chemical reactor so that it provides many of the desired characteristics and advantages of a tubular reactor while maintaining the dimensional compactness and allowing a lower construction cost. Vessel- or tank-*type reactors are known to cause channelling, back-mixing, non-uniform resident time, etc., among a number of other problems such as low linear velocity.
U.S. Pat. No. 2,690,267 issued to Miller et al. discloses a catalyst loading and baffle by which a plurality of baffle plates in the shape of truncated circles are inserted into corresponding grooves inside the reactor to reduce the extent of channelling. The baffled reactor disclosed in the '267 patent does not provide a uniform path length for the reactant molecules. Because of the circular cross-section of the reactor, some reactants travelling near the center of the reactor (horizontally) will have a shorter path length than those travelling near the edge of the reactor, thus resulting in non-uniform resident times for the reactants and possibly low reaction yield and/or side products.
U.S. Pat. No. 3,898,049 issued to Burroughs, et al. discloses a hydrogenation reactor comprising an elongated vertical container and a plurality of vertical baffles dividing the container into a plurality of vertical compartments thus increasing the height-to-width ratio of the reactor and allowing the linear velocity of the flowing reactants to be increased to several times that of a single pass reactor. One of the disadvantages of the compartmentized reactor disclosed in the '049 patent is that, in half of the compartments, the gaseous reactants must travel downward. Furthermore, because all the radially disposed compartments adjoin the same core compartment, leakage may become a concern. Also, the compartments do not have the same cross-sectional areas, thus resulting in non-uniform flow paths for the gas reactants
U.S. Pat. No. 2,127,561 issued to Herman discloses a heat exchange catalytic converter which contains a plurality of paired catalyst passages. The entering gases are led into the reactor which pass upwardly through one set of passages then downwardly through another set of passages. Because of the heat liberated by the exothermic reaction, the catalyst at an inlet zone will be heated by the contiguous catalyst at an exit zone. U.S. Pat. No. 1,945,353 issued to Jaeger discloses a similar multiple-path reactor to effect heat exchange between catalysts in different paths.
U.S. Pat. No. 2,120,538 issued to Andrews discloses a vapor phase oxidation reactor which contains a plurality of staggered shelves, on which is placed a vanadium oxide catalyst. The vapors pass downwardly over the catalyst. U.S. Pat. No. 3,048,468 issued to Watkins discloses a similar catalytic reactor containing a plurality of staggered shelves, on which the catalyst is placed. Inert particles are heated and introduced into the reactor which travel counter-currently to the reactants to effect heat transfer. U.S. Pat. No. 3,506,408 issued to Kageyama, et al., also discloses a reactor containing similarly staggered catalyst shelves.
U.S. Pat. No. 4,590,044 issued to Mos, et al., discloses a multistage reactor containing a number of radially disposed ring-shaped lamellae of two different sizes. The smaller lamellae contact the central inlet tube but do not contact the inner shell of the reactor and the larger lamella contact the inner,shell but do not contact the inlet tube. The smaller lamella alternate with the larger lamella so that a zig-zag path is formed in the reaction space.